A vehicle generally contains automatic safety restraint devices activated during a vehicle crash to reduce occupant injury. The safety of the occupant of a vehicle during a crash depends upon whether or not the occupant is using the safety restraint system, and, if so, whether or not the system is properly adjusted. Examples of automatic safety restraint devices include air bags, seat belt pretensioners, and deployable knee bolsters. A more effective safety restraint system controls the deployment force of airbags and the pretension of seatbelts based on detected characteristics of the seat occupant such as the size of the seat occupant. For example, when an adult is seated on the vehicle seat, the airbag can be deployed in a normal manner; however, if a small child is seated on the seat, the airbag either should not be deployed or should be deployed with a lower deployment force. Sensors of various types are placed at locations in and around the vehicle to detect situational characteristics both inside the vehicle and outside the vehicle. The information from the sensors is input into one or more control unit that controls the function of the safety restraint devices.
Restraint systems such as motorized seat belt (MSB) retractors have become standard equipment in modern automobiles. MSB retractors are widely used to protect passengers from the impact produced during a vehicle collision. Prior to a collision involving the vehicle, the MSB actuates a seat belt to protect the passenger. The MSB could be deployed because there are indications of an impending collision (an emergency situation), based for example on a severe breaking or swerving of the vehicle or external sensor systems that predict a high probability of a collision or of a potential rollover. The MSB could also be deployed at low force levels for comfort related reasons. As a result, the motor control of the MSB may have two basic types of modes, comfort mode and safety mode.
A MSB retractor includes a motor, typically electric, that operates to retract the seat belt in case of an emergency or to assist in the extraction or retraction when a passenger enters or exits the vehicle. The operation of the motor may be controlled by a signal generated by a microprocessor. A control system algorithm and the associated logic are needed to define the different safety and comfort modes that the MSB control unit is designed to fulfill. Such an algorithm should receive multiple sources of information available from various sensors such as a buckle status sensor, a seat track position sensor, a belt movement sensor, etc, and should utilize the information to improve the comfort level and the safety level of the vehicle occupant.